Television



May 22,1928; 1,s7 0,79s'

E. BELIN TELEVISION Filed Nov. 20, 1923 2 Sheets-Sheet 1 May 22, 1928.1,670,795

' E. BELIN TELEVISION Filed Nov. 20. 1 92s 2 she ts-sheet 2 Patented May22, 1928.

. UNITED STATES EDOUABD BELIN, 01; BUEIL, FRANCE.

' TELEVISION.

Application filed Hovember'20 1923, Serial No. 675,915, and in FranceDecember 27, 1988.

cinematograph; it requires-the projection of such a number of selectedluminous or illuminated points of the object to be reproduced that thewhole of this object is ex plored in a time period'such that portions ofthe object cannot become displaced or the object altered to anysubstantial extent; moreover projection should take place with anintensity and a rapidity such that the eye receives a sensation similarto that which it has when looking at the object itself and such thatretinal persistance occurs in order that the sensation may becontinuous.

As television requires exploration and a reconstitution in a very shorttime by a considerable number of points ordinary methods of transmissionas employed in telephonic and telegraphic transmission over line wiresand apparatus connected there with are not capable of answering allrequirements. Continuous waves such as are generated and employed inwireless telegraphy and telephony may, however, be efficiently employedfor line wire or wireless transmission. In the use of a wire, .it isemployed as a director of waves, and such use should be considered ascoming within the scope of the invention.

It is known that waves generated at a transmitting station may bemodulated; in

wireless telephony it is the variation of resistance of the microphonewhich causes such modulation.

For television forming the subject of this invention it has been foundthat an element whose resistance to the passages of the current variesaccording to the degrees of illumination of such element will produce aphenomenon which is very comparable and in some Ways identical withsound modulation.

The solution of the problem of television so far as relates totransmission consists therefore in dividing up the object into adefinite number of points and in causing the graphic ;camera.. There arethus two meth-- ods of operation exploring the optical lmage by thesensitive element or moving the optical image over the stationaryelement.

Without rejectingthe first method it may be said that considerabledifficulty is met within carrying it out. This will be seen from somefigures, which are however very approximative.

' If the optical image similar to that in a cinematograph be taken, thatis of a size 18'X24 mm., it has a surface of 432 millimeter. For'anexploration of 5 the sq. mm. (which is'not excessive as in projectingthere should be 25 points to the sq. mm.) there would be nearly 11000for one image. In a cinematograph at least 10 points to pictures areprojected per second; the num ber of points will thus lie between100,000 and 120,000 persecond.

It will be seen that in order to displace the sensitive member 100,000times per second with apause between the movements, inertia effects willbe encountered which render exploration by the first method inexpedientat the present time.

In thev second method,.the sensitive element remains stationary and maybe of very delicate construction. It may be for example a selenium cellor a photoelectric bulb or other known means. It is only necessary toinsert in the circuit of this cell or lamp a positive or ne ativeresistance proportional or substantia ly proportional (a simple functionor even an exponential function) to the illumination of the sensitiveoint.

A real optical image of the o ject is moved over this point.

a Fig. 1 is a diagrammatical representation of one form of transmitter;Fig. 2 is a modification; Fig. 3 shows a die ammatical representation ofone form 0 receiver; and Fig.4 is a modification thereof.

Referring to Figure 1, it will be seen that if the optical axis of thesighting objective passes through 0 a real optical ima e of theobjective will be formed. at A- This image can be transferred to A B breflecting the emergent rays by a mirror By turni mirror M around itsaxis m the points on a line A B of the image can be brought to a point Slying behind a small of the beam reflected by hole 8 in a diaphragm Splaced at A B: hus this point will be successively illuminated by pointsof the line A B. If however a second mirror M is inter fised in the path1 and is turned about the axis m m it may be in the plane of the figureand at right angles to m then after the movement of a line over S mirrorM may be so displaced that an adjacent line passes over S during thereturn movement of mirror M Thus wholly to explore the image A' BmirrorM must in' the time taken for this exploration) ma e a number ofmovements equal to the number of lines into which the object has beendivided up and mirror M must at each oscillation be displaced throughthe angle required to bring successive lines on to point S. p

In the case under consideration, mirror M should have 90 angulardisplacements and mirror M should make to and fro movements in. the timetaken as the minimum. During this period the sensitive element willmodulate a generator circuit of continuous Waves; this is effected byany method best adapted to the particular circumstances. As indeedeffects of a point like character only come into question each movementof mirror M may be continuous; the modulating effect is therefore reallyworthy of this name, that is it causes a variation without points orjerks in the generatdr circuit. 7

This circuit will therefore emit modulated waves according to theluminous intensity of the image. It should be understood that by thepoint S is meant either'the sensitive cell itself or an optical systemallowing the luminous effect to act upon the cell with power andclearness i. e. the sensitive cell may bemouiited in rear of an opticalsystem similar to an enlarging objective which concentrates or spreadsthat portion of the incident beam which passes diaphragm A B, that iscorrespondin It should also be un erstood that the modulation caused bythe sensitive cell is utilized directly or with the interposition ofsuitable amplifying systems.

The transmitting system just described may be modified by employing themirror of an oscillograph instead of and in place of the mirrors M M,.This variation is illustrated diagrammatically in Figure 2.

Let it be supposed that objective 0 gives an image AB of the object A0B0. By acting on this optical image before its formation with an opticalsystem very similar to a reversed microscope, a reduced image A B willbe produced, then another image A B". By a properselection of the powersof this to an image element.

If an oscillograph scanning mirror M is interposed in front of the planeof the image A" B", the image will be deviated and a microscopearrangement 45 identical with the first will give an imageA' B5 =A Bwhile an'objective 6 will produce an image a B of any size desired. Ifmirror is vibrated by alternating current at a pr determined frequencthe image A' B' will be displaced in its plane.

If at a )3 a converging objective 7 is provided,a sharp image of mirrorM will be obtained at S. A sensitive cell is placed at oscillation ofsuch image, if such aperture is assumed, for purpose of illustration, tobe substantially stationary there will be'a free passage for all theelements of one line of a B at right angles to the axis of oscillationof mirror M. If at the moment at which such line is passed through, i.e. at which the mirror returns, the aperture is displaced throughthespa'ce between one line and the next there will be a free passage forthe elements of another line of a B. The luminous points therefore ofthese two lines will both pass over cell S. The movement of the aperturein front of lens .7 continues for the whole duration of the vibrationsof mirror M, until the entire image has been traversed and all thepoints successively pass over the cell S.

For the example in question the mirror M should receive 45 vibrationsand the point P should make a complete traverse in steps for onecomplete exploration. The variations produced on cell S are as in theformer case not sudden, but on the contrary continuous while modulationalso is absolute. Instead of using a diaphragm with a single'aperture P,there may of course be a continuously moving (rotary) band (shutterdisk) which turns behind S and has in it as many'apertures P as arenecessary for the passagejof the luminous small areas or subdivisions ofthe beam with the required point. In order that the ima e may beloodegree of rapidity. Under such conditions the image is explored by lineswhich are oblique to the direction of deplacement of the aperture Pandnot at right angles, but

to produce a luminous beam whose intensity is proportional orproportioned to such modulation and on the other hand to displace suchbeam according to a law which is extransparency from absolute opacity toabsolute transparency in such a manner that for a maximum deviationproduced by the efl'ects of modulation corresponding to the maximumillumination or no illumination of the transmitting cell S, the stripwill be traversed from the centre to one end. A lens L placed in'thepath of the beam thus varied in intensity produces at E the image of R.A lens L will bring such image to 2 between Ii and Z however-a mirror Ris interposednvhich synchronizes with mirror M Figure 1 of which it isthe replica. The beam is again reflected at right angles by a mirror Rsimilar to mirror M and synchronizing therewith. The screen E receivesan image similar to A B in Figure 1. At ,2, there may be a mirror R asin Figure at. The beam reflected from R, is displaced acording to thedisplacements of R. If however mirror R, is given equal and oppositeangular displacements to those of mirror R the reflected beam will befixed.

The beam then falls on a lens R which concentrates it upon a mirror .R,to which movements are imparted inv synchronism with those of mirror M(Figure 1). At E a stationary line is produced whose points will vary inintensity. As in Figure 1 a mirror R having movements synchronizing withthose of M will impart to such line displacements in a direction atright angles to its lengtln. It will therefore be seen that inbotharrangements successive and upwardly' moving lines, appear on screen E.If projection is effected at a speed such that retinal 'persistanceoccurs and that visual acuteness is not exceeded a spectator will seethe whole image'on the screen E, while if the images succeeded oneanother sufiiciently rapidly for the efi'ect of persistence to bemaintained, projection will be continuous and will effectively representthe objects at the transmitting station.

synchronism of mirrors M M, R R R, B, may be obtained by simple and suremeans, for exam leby means of a wave superimposed on t e modulated wavebut of different length. The manner of mechanically connecting M and M,'R and R and ning element for scanning said R and R, in order tomaintain synchronism by a single synchronizing current is an obviousmechanical expedient and does not come within the scope of theinvention.

In the same manner any arrangement may be adopted which allows theluminosity of projection to be increased.

It is easy to conceive a modification which can readily be carried intoelfect; thus modulation at the receiver may be employed to cause, bymodifying a transverse field, the deviation of a cathode ray controlledin 0. Braun tube as has been done for making a cathode ray oscillograph.

The illumination of the screen may be varied by a suitable screen (oflead or other opaquematerial of a graduated thickness or opacity); theluminous efl'ect on the screen may. be caught either by a rotatingmirror with an exploration system similar to that above described oreven by a film which is exposed, developed and projected immediately,which willonly cause the reproduction to lag behind the actual objectfor a relatively. short time which time is always constant; the Kerrphenomenon or any other phenomenon which give rise to displacements ofluminous beams by electromagnetic or static effects may be employed.

" Having now particularly described and ascertained the nature of mysaid invention and in what manner the same is to be performed, I declarethat what I claim is:

1. In a television system, means for producing, in a single plane, anoriginal luminous image and a reduction thereof, a photosensitiveelement, an oscillograph mirror operative to'scan the reduced image andto deflect the same angularly from its plane into a plane extendlng on astrai ht line between the oscillograph mirror an the photosensitiveelement, means in the latter-named plane for enlarging the deflectedimage, and a scanning device operative angularly of the lane of theenlarged portion of the de ected image for scanning the same andgoverning the passage of the minous points thereof to the photosensitiveelement.

2. In a television system, an ima e, means for projecting said image topro uce said image of smaller dimensions than said original image,scanning means for scaning said smaller image, means for projecting saidimage a second'time to produce an image of larger dlmensions and asecond scanner for scanning said image of increased dimensions.

3. In a television system, a luminous image, a series of lenses, fordecreasing the dimensions of said image, means for scanning said ima eof smaller dimensions, a second series o lenses for increasing thedimensions of said image and a second scanimage of increased dimensions.

4. In a television system, a fixed source of light, a deflecting memberdeflected in accordance with the variations of received can said lightto pass in accordance with the extent of deflection thereof, and asecond deflecting member arramged to deflect for distances-proportionalto the deflection of said first deflecting member whereby the path ofsaid beam of light remains the some irrespective of'the deflection ofsaid first deecting member.

5. In a receiver, a beam of light, means for deflecting said beam from apredetermined path in accordance with received current and a secondmovable means operated in c0njunc-= tion with sand first means fordeflecting said beam in opposite direction from said first deflectionand scanning means for moving seid'beam over a surface.

EDUARD BELEN.

